i'm sorry flours this is happening to you. i'm not a depressive (or at least not clinically) - so i may lack understanding of all your difficulties. if i say something inappropriate or stupid, please let me know.
the only adage i can offer is 'be true to yourself'. - you sound like you are still trying w/ all your might to live up to all those other people's expectations and that is making the whole situation worse. your mother giving you current events to have conversations you'd rather not, making you the designated driver, people basically hounding you for info, etc. and you feel bad for even thinking of leaving early - and you're even thinking of getting somehow disfigured so your outside body agrees w/ your inner mental turmoil.
but to keep on 'putting on a front' will only make the other people's expectations continue to exist. but you love all these people right? the problem sounds more like you can't stand the noise or personal bodily involvement or all the action that's going on. if you could be alone w/ each person that has bothered you - in a quiet place just to share a moment - would that bother you too?
if both your parents and your aunt and all their friends are extraverts and you're the only introvert - to me that sounds like torture. but somehow you have to take care of yourself and somehow tell all those people that all the celebrating is very taxing on you and you're having difficulty w/ the whole activity.
you can either continue to put up a front till it robs you of yourself - or tell people gradually one by one, that all this excitement and celebrating is hurting and panicking you. you may be surprised to find out that some other people there are doing the exact same thing as you.